When you con?¬?gure an IPsec
gateway to provide security services, you must ?¬?rst choose an IPsec protocol. The choices are
ESP or ESP with AH. The second square is an encryption algorithm. Choose the encryption
algorithm that is appropriate for the desired level of security: DES, 3DES, or AES. The third
square is authentication. Choose an authentication algorithm to provide data integrity: MD5 or
SHA. The last square is the DH algorithm group. Choose which group to use: DH1, DH2, or
DH5. IPsec provides the framework, and the administrator chooses the algorithms that are used
to implement the security services within that framework.
Summary of Introducing VPN Solutions
The following summarizes the key points that were discussed in the previous sections:
?– Organizations implement VPNs because they are less expensive, more secure, and
easier to scale than traditional WANs.
?– Site-to-site VPNs secure traf?¬?c between intranet and extranet peers. Remote-access
VPNs secure communications from the traveling telecommuter to the central of?¬?ce.
?– VPNs can be implemented with a variety of different Cisco devices??”Cisco IOS
routers, ASA 5500 Series adaptive security appliances, and Cisco VPN Client
software.
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